Obesity, physical activity influence subsequent neoplasm risk in childhood cancer survivors

Obesity contributes to an increased risk of multiple subsequent neoplasms in childhood cancer survivors, but higher physical activity confers a protective effect, according to a retrospective study.

Researchers looked at 5-year childhood cancer survivors who had received their diagnosis before they turned 21 years of age from the Childhood Cancer Survivor Study (CCSS). Self-reported time-varying BMI and maximum reported physical activity (measured as metabolic equivalent of task h/week [MET-h/week]) before any subsequent neoplasm development were assessed at cohort entry and up to six times thereafter.

The primary outcome was the cumulative incidence of subsequent neoplasms, evaluated by physical activity level and time-varying BMI categories.

There were 25,658 enrolled CCSS participants identified, of which 22,716 had BMI data before subsequent neoplasm development and met the eligibility criteria for the study (median attained age 33.7 years, 46.3 percent female). A total of 2,554 subsequent neoplasms occurred among 2,156 individuals (median age at subsequent neoplasm diagnosis 37.4 years, 56.7 percent female).

The 30-year subsequent neoplasm cumulative incidence was higher among survivors reporting lower physical activity (18.6 percent for 0 MET-h/week vs 10.9 percent for 15-21 MET-h/week). Those with BMI in the obese category had higher incidence rates of solid organ (relative rate [RR], 1.22, 95 percent confidence interval [CI], 1.01–1.46), central nervous system (RR, 1.47, 95 percent CI, 1.12–1.95), and skin (RR, 1.30, 95 percent CI, 1.13–1.50) subsequent neoplasms.

Of note, higher physical activity (15–21 MET-h/week) showed a protective association with any (RR, 0.61, 95 percent CI, 0.53–0.71), solid organ (RR, 0.65, 95 percent CI, 0.52–0.83), CNS (RR, 0.50, 95 percent CI, 0.35–0.70), and skin (RR, 0.72, 95 percent CI, 0.60–0.86) subsequent neoplasms.

BMI and physical activity were specifically associated with subsequent meningiomas and thyroid carcinomas but not with breast/colorectal cancers and haematologic subsequent neoplasms.

The findings underscore the need to consider lifestyle interventions in future subsequent neoplasm prevention research.